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Yasui H, Iizuka D, Hiraoka W, Kuwabara M, Matsuda A, Inanami O. Nucleoside analogs as a radiosensitizer modulating DNA repair, cell cycle checkpoints, and apoptosis. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2019; 39:439-452. [PMID: 31560250 DOI: 10.1080/15257770.2019.1670839] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The combination of low dose of radiation and an anticancer drug is a potent strategy for cancer therapy. Nucleoside analogs are known to have a radiosensitizing effects via the inhibition of DNA damage repair after irradiation. Certain types of nucleoside analogs have the inhibitory effects on RNA synthesis, but not DNA synthesis, with multiple functions in cell cycle modulation and apoptosis. In this review, the most up-to-date findings regarding radiosensitizing nucleoside analogs will be discussed, focusing especially on the mechanisms of action.
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Affiliation(s)
- Hironobu Yasui
- Laboratory of Radiation Biology, Department of Applied Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Daisuke Iizuka
- Department of Radiation Effects Research, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Wakako Hiraoka
- Laboratory of Biophysics, School of Science and Technology, Meiji University, Kawasaki, Japan
| | - Mikinori Kuwabara
- Laboratory of Radiation Biology, Department of Applied Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Akira Matsuda
- Center for Research and Education on Drug Discovery, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Osamu Inanami
- Laboratory of Radiation Biology, Department of Applied Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan
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Saito S, Hasegawa S, Sekita A, Bakalova R, Furukawa T, Murase K, Saga T, Aoki I. Manganese-enhanced MRI reveals early-phase radiation-induced cell alterations in vivo. Cancer Res 2013; 73:3216-24. [PMID: 23695553 DOI: 10.1158/0008-5472.can-12-3837] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
For tumor radiotherapy, the in vivo detection of early cellular responses is important for predicting therapeutic efficacy. Mn(2+) is used as a positive contrast agent in manganese-enhanced MRI (MEMRI) and is expected to behave as a mimic of Ca(2+) in many biologic systems. We conducted in vitro and in vivo MRI experiments with Mn(2+) to investigate whether MEMRI can be used to detect cell alterations as an early-phase tumor response after radiotherapy. Colon-26 cells or a subcutaneously grafted colon-26 tumor model were irradiated with 20 Gy of X-rays. One day after irradiation, a significant augmentation of G2-M-phase cells, indicating a cell-cycle arrest, was observed in the irradiated cells in comparison with the control cells, although both early and late apoptotic alterations were rarely observed. The MEMRI signal in radiation-exposed tumor cells (R1: 0.77 ± 0.01 s(-1)) was significantly lower than that in control cells (R1: 0.82 ± 0.01 s(-1)) in vitro. MEMRI signal reduction was also observed in the in vivo tumor model 24 hours after irradiation (R1 of radiation: 0.97 ± 0.02 s(-1), control: 1.10 ± 0.02 s(-1)), along with cell-cycle and proliferation alterations identified with immunostaining (cyclin D1 and Ki-67). Therefore, MEMRI after tumor radiotherapy was successfully used to detect cell alterations as an early-phase cellular response in vitro and in vivo.
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Affiliation(s)
- Shigeyoshi Saito
- Department of Medical Physics and Engineering, Division of Medical Technology and Science, Faculty of Health Science, Graduate School of Medicine, Osaka University, Osaka, Japan
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Tsao A, Hui EP, Juergens R, Marur S, Huat TE, Cher GB, Hong RL, Hong WK, Chan ATC. Phase II study of TAS-106 in patients with platinum-failure recurrent or metastatic head and neck cancer and nasopharyngeal cancer. Cancer Med 2013; 2:351-9. [PMID: 23930212 PMCID: PMC3699847 DOI: 10.1002/cam4.79] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/06/2013] [Accepted: 03/14/2013] [Indexed: 11/09/2022] Open
Abstract
TAS-106, a RNA polymerase inhibitor, was studied in solid tumors with potential clinical benefit and reasonable tolerability. We conducted a multicenter, international phase II trial of TAS-106 in salvage metastatic or recurrent head and neck squamous cell cancer (HNSCC) and nasopharyngeal cancer (NPC) patients. TAS-106 monotherapy was given at 6.5 mg/m2 over 24-h continuous infusion every 3 weeks. Translational studies for blood and tissue were included. Twenty-seven enrolled patients experienced the most common drug-related adverse events of neutropenia, fatigue, non-neutropenic fever, injection site reaction, and skin rash/dermatitis. The greater than or equal to grade 3 adverse events included neutropenia (14.8%), febrile neutropenia (7.4%), pneumonia (7.4%), and peripheral neuropathy (3.7%). The overall response rate was 0% in both subgroups; five HNSCC patients had stable disease (median duration 99 days) and four NPC patients had stable disease (median duration of 92.5 days). Median progression-free survival (PFS) for HNSCC patients was 52 days (95% CI 43.0–99.0 days) and 48 days (95% CI 41.0–83.0 days) for NPC. Median overall survival (OS) for HNSCC patients was 175 days (95% CI 92.0–234.0 days) and 280 days (95% CI 107.0–462.0 days) for NPC. The TAS-106 plasma levels were equivalent between Asian and Caucasian patients. There was no significant correlation of tumor UCK2 protein expression levels to TAS-106 efficacy. TAS-106 was reasonably tolerated in patients with platinum-failure HNSCC and NPC. The administration schedule of 24-h continuous infusion prevented neurologic toxicity, but had myelosuppression as its main toxicity. There was no anti-tumor efficacy seen with TAS-106 monotherapy. Future studies will focus on TAS-106 combinations and mechanisms of drug resistance.
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Affiliation(s)
- Anne Tsao
- Department of Thoracic and Head and Neck Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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Meike S, Yamamori T, Yasui H, Eitaki M, Matsuda A, Morimatsu M, Fukushima M, Yamasaki Y, Inanami O. A nucleoside anticancer drug, 1-(3-C-ethynyl-β-D-ribo-pentofuranosyl)cytosine (TAS106), sensitizes cells to radiation by suppressing BRCA2 expression. Mol Cancer 2011; 10:92. [PMID: 21798026 PMCID: PMC3161955 DOI: 10.1186/1476-4598-10-92] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 07/28/2011] [Indexed: 11/30/2022] Open
Abstract
Background A novel anticancer drug 1-(3-C-ethynyl-β-D-ribo-pentofuranosyl)cytosine (ECyd, TAS106) has been shown to radiosensitize tumor cells and to improve the therapeutic efficiency of X-irradiation. However, the effect of TAS106 on cellular DNA repair capacity has not been elucidated. Our aim in this study was to examine whether TAS106 modified the repair capacity of DNA double-strand breaks (DSBs) in tumor cells. Methods Various cultured cell lines treated with TAS106 were irradiated and then survival fraction was examined by the clonogenic survival assays. Repair of sublethal damage (SLD), which indicates DSBs repair capacity, was measured as an increase of surviving cells after split dose irradiation with an interval of incubation. To assess the effect of TAS106 on the DSBs repair activity, the time courses of γ-H2AX and 53BP1 foci formation were examined by using immunocytochemistry. The expression of DNA-repair-related proteins was also examined by Western blot analysis and semi-quantitative RT-PCR analysis. Results In clonogenic survival assays, pretreatment of TAS106 showed radiosensitizing effects in various cell lines. TAS106 inhibited SLD repair and delayed the disappearance of γ-H2AX and 53BP1 foci, suggesting that DSB repair occurred in A549 cells. Western blot analysis demonstrated that TAS106 down-regulated the expression of BRCA2 and Rad51, which are known as keys among DNA repair proteins in the homologous recombination (HR) pathway. Although a significant radiosensitizing effect of TAS106 was observed in the parental V79 cells, pretreatment with TAS106 did not induce any radiosensitizing effects in BRCA2-deficient V-C8 cells. Conclusions Our results indicate that TAS106 induces the down-regulation of BRCA2 and the subsequent abrogation of the HR pathway, leading to a radiosensitizing effect. Therefore, this study suggests that inhibition of the HR pathway may be useful to improve the therapeutic efficiency of radiotherapy for solid tumors.
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Affiliation(s)
- Shunsuke Meike
- Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan
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Meike S, Yamamori T, Yasui H, Eitaki M, Matsuda A, Inanami O. 8-Aminoadenosine enhances radiation-induced cell death in human lung carcinoma A549 cells. JOURNAL OF RADIATION RESEARCH 2011; 52:456-463. [PMID: 21785234 DOI: 10.1269/jrr.10188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The combination of a chemotherapeutic agent and radiation is widely applied to enhance cell death in solid tumor cells in cancer treatment. The purine analogue 8-aminoadenosine (8-NH(2)-Ado) is known to be a transcription inhibitor that has proved very effective in multiple myeloma cell lines and primary indolent leukemia cells. In this report, to examine whether 8-NH(2)-Ado had the ability to enhance the radiation-induced cell killing in solid tumor cells, human lung adenocarcinoma A549 cells were irradiated in the presence and absence of 8-NH(2)-Ado. 8-NH(2)-Ado significantly increased reproductive cell death and apoptosis in A549 cells exposed to X-rays. When peptide inhibitors against caspase-3, -8, and -9 were utilized to evaluate the involvement of caspases, all inhibitors suppressed the enhancement of radiation-induced apoptosis, suggesting that not only mitochondria-mediated apoptotic signal transduction pathways but also death receptor-mediated pathways were involved in this enhancement of apoptosis. In addition, in the cells exposed to the treatment combining X-irradiation and 8-NH(2)-Ado, reduction of the intracellular ATP concentration was essential for survival, and down-regulation of the expression of antiapoptotic proteins such as survivin and XIAP was observed. These results indicate that 8-NH(2)-Ado has potential not only as an anti-tumor drug for leukemia and lymphoma but also as a radiosensitizing agent for solid tumors.
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Affiliation(s)
- Shunsuke Meike
- Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Japan
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Lui VWY, Lau CPY, Cheung CSF, Ho K, Ng MHL, Cheng SH, Hong B, Tsao SW, Tsang CM, Lei KIK, Yamasaki Y, Mita A, Chan ATC. An RNA-directed nucleoside anti-metabolite, 1-(3-C-ethynyl-beta-d-ribo-pentofuranosyl)cytosine (ECyd), elicits antitumor effect via TP53-induced Glycolysis and Apoptosis Regulator (TIGAR) downregulation. Biochem Pharmacol 2010; 79:1772-80. [PMID: 20219441 DOI: 10.1016/j.bcp.2010.02.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 02/09/2010] [Accepted: 02/17/2010] [Indexed: 10/19/2022]
Abstract
1-(3-C-ethynyl-beta-d-ribo-pentofuranosyl)cytosine (ECyd) is a ribose-modified nucleoside analog of cytidine with potent anticancer activity in several cancers. The main antitumor mechanism of this promising RNA-directed nucleoside anti-metabolite is efficient blockade of RNA synthesis in cancer cells. Here, we examined the therapeutic potential of this RNA-directed anti-metabolite in in vitro models of nasopharyngeal cancer (NPC). In a panel of 6 NPC cell lines, ECyd effectively inhibited cellular proliferation at nM concentrations (IC(50): approximately 13-44nM). Moreover, cisplatin-resistant NPC cells were highly sensitive to ECyd (at nM concentration). The ECyd-mediated growth inhibition was associated with G(2)/M cell cycle arrest, PARP cleavage (a hallmark of apoptosis) and Bcl-2 downregulation, indicating induction of apoptosis by ECyd in NPC cells. Unexpectedly, ECyd-induced significant downregulation of TIGAR, a newly described dual regulator of apoptosis and glycolysis. More importantly, this novel action of ECyd on TIGAR was accompanied by marked depletion of NADPH, the major reducing power critically required for cell proliferation and survival. We hypothesized that ECyd-induced TIGAR downregulation was crucially involved in the antitumor activity of ECyd. Indeed, overexpression of TIGAR was able to rescue NPC cells from ECyd-induced growth inhibition, demonstrating a novel mechanistic action of ECyd on TIGAR. We demonstrated for the first time that an RNA-directed nucleoside analog, ECyd, exerts its antitumor activity via downregulation of a novel regulator of apoptosis, TIGAR. Moreover, ECyd may represent a novel therapy for NPC.
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Affiliation(s)
- Vivian Wai Yan Lui
- Cancer Drug Testing Unit, State Key Laboratory in Oncology in Southern China, Sir Y.K. Pao Center for Cancer, Department of Clinical Oncology, Hong Kong Cancer Institute and Li Ka Shing Institute for Health Sciences, Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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Purvalanol A induces apoptosis and downregulation of antiapoptotic proteins through abrogation of phosphorylation of JAK2/STAT3 and RNA polymerase II. Anticancer Drugs 2008; 19:565-72. [PMID: 18525315 DOI: 10.1097/cad.0b013e3282fe330e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To clarify the mechanisms of purvalanol A in the induction of apoptosis, we investigated whether purvalanol A influenced the RNA synthesis and expression of RNA polymerase II and signal transducer and activator of transcription 3 (STAT3). When MKN45 cells were treated with 30 micromol/l purvalanol A, mitochondrial dysfunction occurred before the induction of the apoptosis and the expression of antiapoptotic proteins survivin, Bcl-XL, and Bcl-2 was reduced. The treatment with parvalanol A was also shown to reduce not only mRNA for these proteins but also global RNA synthesis. The phosphorylation of the carboxy-terminal domain of RNA polymerase II, which was involved in transcriptional regulation, was strongly inhibited by purvalanol A, followed by the partial inhibition of the expression of RNA polymerase II. Furthermore, the phosphorylation at Tyr705 of STAT3, which is known to be a phosphorylation site for Janus kinase 2 (JAK2), was completely inhibited by purvalanol A early (3 h) after drug treatment, although the phosphorylation of STAT3 at Ser727, which is a phosphorylation site for Ras/Raf/MEK and extracellular signal-regulated protein kinase 1/2, was still detectable until late (12 h) after treatment. In addition, the tyrosine phosphorylation of JAK2 was efficiently inhibited by purvalanol A. These results suggest that the inhibition of JAK2/STAT3 and RNA polymerase II is crucial in the downregulation of antiapoptotic proteins leading to the apoptotic cell death induced by parvalanol A.
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Inhibition of HIF-1alpha by the anticancer drug TAS106 enhances X-ray-induced apoptosis in vitro and in vivo. Br J Cancer 2008; 99:1442-52. [PMID: 18854835 PMCID: PMC2579694 DOI: 10.1038/sj.bjc.6604720] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In a previous study, we showed that a novel anticancer drug, 1-(3-C-ethynyl-β-D-ribo-pentofuranosyl)cytosine (TAS106, ECyd) increased the antitumour efficacy of X-irradiation. However, its effects on hypoxic cells in tumours remain unclarified. Here, we show that TAS106 enhances the induction of apoptosis in X-irradiated human gastric adenocarcinoma MKN45 and MKN28 cells under hypoxia in vitro. At the same time, the accumulation of HIF-1α observed under hypoxia was shown to be decreased to the level of normoxia in the presence of 0.1 μM TAS106. To study the function of HIF-1α protein in apoptosis of hypoxic cells, we employed an HIF-1α reductive approach using its specific antisense oligodeoxynucleotide. The reduction of HIF-1α gene expression dramatically enhanced X-ray-induced apoptosis in hypoxic cells. In in vivo experiments in which MKN45 cells were transplanted into severe combined immunodeficient (SCID) mice, TAS106 (0.5 mg kg−1) suppressed HIF-1α expression and subsequently reduced the area of the hypoxic region in the tumour and enhanced the induction of apoptosis in the hypoxic region when combined with 2 Gy of X-irradiation. These results suggest the possibility that TAS106 acts as a potent radiosensitiser through the inhibition of HIF-1α expression and can be a useful agent against radiotherapy-resistant hypoxic cells in solid tumours.
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Ogura A, Watanabe Y, Iizuka D, Yasui H, Amitani M, Kobayashi S, Kuwabara M, Inanami O. Radiation-induced apoptosis of tumor cells is facilitated by inhibition of the interaction between Survivin and Smac/DIABLO. Cancer Lett 2008; 259:71-81. [DOI: 10.1016/j.canlet.2007.09.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 09/24/2007] [Accepted: 09/24/2007] [Indexed: 11/30/2022]
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Yasui H, Inanami O, Asanuma T, Iizuka D, Nakajima T, Kon Y, Matsuda A, Kuwabara M. Treatment combining X-irradiation and a ribonucleoside anticancer drug, TAS106, effectively suppresses the growth of tumor cells transplanted in mice. Int J Radiat Oncol Biol Phys 2007; 68:218-28. [PMID: 17448876 DOI: 10.1016/j.ijrobp.2006.12.061] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2006] [Revised: 12/23/2006] [Accepted: 12/25/2006] [Indexed: 01/14/2023]
Abstract
PURPOSE To examine the in vivo antitumor efficacy of X-irradiation combined with administration of a ribonucleoside anticancer drug, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine (TAS106, ECyd), to tumor cell-transplanted mice. METHODS AND MATERIALS Colon26 murine rectum adenocarcinoma cells and MKN45 human gastric adenocarcinoma cells were inoculated into the footpad in BALB/c mice and severe combined immunodeficient mice, respectively. They were treated with a relatively low dose of X-irradiation (2 Gy) and low amounts of TAS106 (0.1 mg/kg and 0.5 mg/kg). The tumor growth was monitored by measuring the tumor volume from Day 5 to Day 16 for Colon26 and from Day 7 to Day 20 for MKN45. Histologic analyses for proliferative and apoptotic cells in the tumors were performed using Ki-67 immunohistochemical and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. The expression of survivin, a key molecule related to tumor survival, was assessed by quantitative polymerase chain reaction and immunohistochemical analysis. RESULTS When X-irradiation and TAS106 treatment were combined, significant inhibition of tumor growth was observed in both types of tumors compared with mice treated with X-irradiation or TAS106 alone. Marked inhibition of tumor growth was observed in half of the mice that received the combined treatment three times at 2-day intervals. Parallel to these phenomena, the suppression of survivin expression and appearance of Ki-67-negative and apoptotic cells were observed. CONCLUSIONS X-irradiation and TAS106 effectively suppress tumor growth in mice. The inhibition of survivin expression by TAS106 is thought to mainly contribute to the suppression of the tumor growth.
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Affiliation(s)
- Hironobu Yasui
- Laboratory of Radiation Biology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
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Iizuka D, Inanami O, Kashiwakura I, Kuwabara M. Purvalanol A Enhances Cell Killing by Inhibiting Up-Regulation of CDC2 Kinase Activity in Tumor Cells Irradiated with High Doses of X Rays. Radiat Res 2007; 167:563-71. [PMID: 17474786 DOI: 10.1667/rr0622.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2006] [Accepted: 11/17/2006] [Indexed: 11/03/2022]
Abstract
To clarify the relationship between CDC2 kinase activity and radiation-induced apoptosis, we examined whether the cyclin-dependent kinase (CDK) inhibitor purvalanol A enhanced radiation-induced apoptosis in gastric tumor cells. MKN45 cells exposed to 20 Gy of X rays increased the CDC2 kinase activity and the expression of regulatory proteins (phospho-CDC2 and cyclin B1) of the G2/M phase, followed by activation of the G2/M checkpoint, whereas the treatment of X-irradiated MKN45 cells with 20 microM purvalanol A suppressed the increase in the CDC2 kinase activity and expression of the G2/M-phase regulatory proteins and reduced the fraction of the cells in the G2/M phase in the cell cycle. Furthermore, this treatment resulted in not only a significant increase in radiation-induced apoptosis but also the loss of clonogenicity in both MKN45 (p53-wild) and MKN28 (p53-mutated) cells. The expression of anti-apoptosis proteins, inhibitor of apoptosis protein (IAP) family members (survivin and XIAP) and BCL2 family members (Bcl-X(L) and Bcl-2), in purvalanol A-treated cells with and without X rays was significantly lower than for cells exposed to X rays alone. These results suggest that the inhibition of radiation-induced CDC2 kinase activity by purvalanol A induces apoptosis through the enhancement of active fragments of caspase 3.
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Affiliation(s)
- Daisuke Iizuka
- Laboratory of Radiation Biology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan
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Ichikawa S, Minakawa N, Shuto S, Tanaka M, Sasaki T, Matsuda A. Synthesis of 3′-β-carbamoylmethylcytidine (CAMC) and its derivatives as potential antitumor agents. Org Biomol Chem 2006; 4:1284-96. [PMID: 16557317 DOI: 10.1039/b517602f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
3'-beta-Carbamoylmethylcytidine (CAMC) and its derivatives were synthesized using an intramolecular Reformatsky-type reaction promoted by SmI2 as the key step. In vitro tumor cell growth inhibitory activity was evaluated and CAMC was found to exhibit potent cytotoxicity against various human tumor cell lines. From a structure-activity relationship study it was postulated that the cytotoxic mechanism of action of CAMC did not require phosphorylation at the 5'-hydroxyl group. This study provides a novel strategy for the development of a new type of antitumor nucleoside.
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Affiliation(s)
- Satoshi Ichikawa
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi 6, Kita-ku, Sapporo, 060-0812, Japan
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Iizuka D, Inanami O, Matsuda A, Kashiwakura I, Asanuma T, Kuwabara M. X irradiation induces the proapoptotic state independent of the loss of clonogenic ability in Chinese hamster V79 cells. Radiat Res 2005; 164:36-44. [PMID: 15966763 DOI: 10.1667/rr3393] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The clonogenic ability (reproductive cell death) of Chinese hamster V79 cells was measured after treatment with X radiation and a newly developed anti-cancer drug, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine (ECyd, TAS106). Amplification in the loss of clonogenicity was observed compared to that obtained for cells exposed to X rays alone. Addition of benzyloxycarbonyl-val-ala-asp-fluoromethylketone (Z-VAD-FMK), a broad-spectrum caspase inhibitor, attenuated the increased lethality, but the dose-response curve obtained was found to merely revert to that obtained for cells exposed to X rays alone. Flow cytometric analysis showed that the number of cells arrested at the G2/M phase by X irradiation was decreased by co-treatment with TAS106, and instead the number of cells in the sub-G1 phase increased. Western blot analysis proved that TAS106 treatment down-regulated the expression of the G2/M arrest-related proteins cyclin B1, phospho-CDC2 and WEE1. From these results, it was concluded that (1) no apoptosis was included in the dose-response curve obtained from cells exposed to X rays alone, (2) X radiation induced a potentially apoptotic (proapoptotic) state in cells independent of the loss of their clonogenic ability, and (3) TAS106 enhanced the loss of their clonogenic ability by converting the proapoptotic cells to apoptotic cells through the abrogation of arrest at the G2/M phase.
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Affiliation(s)
- Daisuke Iizuka
- Laboratory of Radiation Biology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan
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